Subject: Re: [mobile-ip] Mipv6 issue #126: exponential back-off vs. rate limiting

From: "Krishna Kumar" <[email-masked]>
Date: Fri, 27 Sep 2002 14:23:06 -0700

Hi Jari,

Does this mean that if a MN gets tunneled packet, it still uses
exponential back-off mechanism to send BU's to the CN ? There
is a problem with the new proposal, viz :

If the CN got the BU after say 128 seconds (ACK bit was set), and
then the CN crashed, when it comes back up and interracts with
the MN, it sends packets to the MN's home address which gets
tunneled via the Home Agent. So the MN re-starts RR, but after
successful RR, it is not able to send the BU till another 256 seconds
have passed from the last time a BU was sent.

So I think that for tunneled-packet-receive, the MN should send the
BU to the CN based on rate limiting, not using back-off, since the later
can introduce a lot of delays.

I hope I have not misunderstood anything here :-)

thanks,

- KK

                      Jari Arkko                                                                                                                 
                      <[email-masked]>        To:       "[email-masked]'" <[email-masked]>                
                      Sent by:                        cc:                                                                                        
                      owner-mobile-ip@sunroof.        Subject:  [mobile-ip] Mipv6 issue #126: exponential back-off vs. rate limiting             
                      eng.sun.com                                                                                                                

                      09/27/2002 12:54 PM                                                                                                        

(Originally brought up by Conny Larsson)

Draft 18 has an exponential back-off mechanism to
send BUs at 1 s, 2 s, 4 s, 8 s and so on intervals
until a BA is received or 256 s is reached.

But it also has a rate-limiting procedure to avoid
sending more than 5 BUs at 1 s intervals and then
any number of BUs at 10 s intervals.

These two procedures seem to be in conflict and
may duplicate functionality. The conflict
arises if rate-limiting would allow sending 5 BUs
in 5 seconds, while the exponential back-off would
allow only 3. Could these procedures be combined?
Perhaps exponential back-off would be sufficient
by itself (maybe with a lower maximum time than 256
seconds).

The same applies to return routability messages.

BE rate limitation is as it should be (references
ICMP). BRR rate limitation must be applied, but
there is no indication of what kind of rate
limitation to use. This should be specified.

Jari